Inhibition of crystallization of liquid epoxy resins

ABSTRACT

Liquid epoxy resins are stabilized against crystallization at ambient temperatures by combining therewith a crystallization inhibiting amount of 2-amino-2-ethyl-1,3-propanediol.

United States atent Haugh 1 1 May 30, 1972 [54] INHIBITION OF CRYSTALLIZATION 3,477,981 11/1969 De Hoff et a1 ..260/31.2 R

0F LIQUID EPOXY RESINS FOREIGN PATENTS OR APPLICATIONS [72] 1,137,863 11/1962 Germany ..260/47 EN [73] Assignee: General Mills Chemicals, Inc.

Primary Examiner .lul1us F rome Filed; 1970 Assistant Examiner-Arthur H. Koeckert Attorney-Anthony A. Juettner, Patrick J. Span and William [21] App]. No.. 80,199 C. Babcock 521 US. Cl. .....260/29.2 EP, 260/47 EP [57] ABSTRACT Illl- 8 53/00 8 30/ 14 Liquid epoxy resins are stabilized against crystallization at am- Field of Search 360/584, EP, 47 EP, 47 EN bient temperatures by combining therewith a crystallization inhibiting amount of 2-amino-2-ethyl- 1 ,3-propanediol. [56] References Cited 7 Claims, No Drawings UNITED STATES PATENTS 3,051,681 8/1962 Partansky ..260/47 EP INHIBITION OF CRYSTALLIZATION F LIQUID EPOXY 1,1 ,4,4-tetrakis(hydroxyphenyl) butane, 1, l ,4,4- RESINS tetrakis(hydroxyphenyl)-2-ethylbutane and the like. The

This invention relates to liquid epoxy resins and their staepoxy resin reaction product of epichlorohydrin and bilization against crystallization. This stabilization or inhibitetraphenol may be represented by the following theoretical tion of crystallization is accomplished by combining with the 5 struetural formula:

liquid epoxy resin a small, but elrective, amount of 2-arnino-2- where R is a tetravalent aliphatic hydrocarbon chain having ethyl-1,3-propanediol. 1 5 from two to 10, and preferably, from two to six carbon atoms. It is known that liquid epoxy resins now supplied have a ten- In general, the epoxy resins may be described as those havdency to crystallize on standing at ambient temperatures. This ing terminal epoxide groups and being liquid at normal room tendency is increased by storage under fluctuating temperatemperature, i.e. about C. ture conditions and the introduction of solvents, reactive I dditio th ox resin may b characterized furth diluents and fillers. Recently, aqueous emulsions 0f epoxy 20 by reference to their epoxy equivalent weight, the epoxy resins have found wide application. The introduction of water equivalent weight of pure epoxy resin b i h mean molecuihte the hqutd epoxy resins has greatly increased the tendency lar weight of the resins divided by the mean number of epoxy t0 crystallization and Presently khewh inhibitors have hot radicals per molecule, or in any case, the number of grams of been satisfactorily effective, Particularly in the aqueous epoxy equivalent to one epoxy group or one gram equivalent systems.

The problem of crystallization of the diglycidyl ethers of bisphenol A has been recognized in the art. US. Pat. No. 3,051,681 discloses the use of a polyglycidyl ether of a novolak resin containing 2-5 phenolic hydroxyl groups as a crystallization inhibitor. This method has the disadvantage of requiring relatively large amounts of the inhibitor. Continued 2 of epoxide. With the most common epoxy resins, the diglycidyl ether of bisphenol A, the liquid resins will have epoxy equivalent weights of about 140-300.

The inhibitor is used in a small amount, generally from 0.02 up to about 3, and more desirably 0.05 to about 1 part per 100 parts of resin (phr.). This amount is sufficient to inhibit research efforts for more effective crystallization inhibitors crystallization of the epoxy resins at ambient temperatures but can be further seen from Us 3 477 981 which insufficient to change significantly the weight per epoxide of ploys trismydroxymethyl) amino methane as a crystallization the epoxy resin or the physical properties of the resins when inhibitor. This inhibitor has the disadvantage ofdarkening the P Thepmferred level with the diglycidyl ethers epoxy resin particularly if overheating takes place during blsphenolAls about blending Ofthe liquid epoxy resin and inhibimn The preferred method of blending the inhibitor With the The inhibitor of the present invention has been found to be hquld epoxy reslh is e h the le y reslh to about a more ff ti epoxy crystallization inhibitor than those before adding the inhibitor. The inhibitor which is a liquid ditives presently in common use and is effective to stabilize 40 blends easily with the liquid p y resihsome instances, aqueous emulsions of the epoxy resin against rystallizatior the initial mixture may be cloudy but clears as the inhibitor iS The inhibitor is more effective in fonnu|a[ed epoxy paints added or after a short time at the elevated temperature, i.e. than the commonly used stabilizers. in addition, the inhibitor b t 5 in te a 125C. The inhibitor has no effect on the is easy to blend with liquid epoxy resins. color of the epoxy resin, even if overheating should take place,

This invention is useful with liquid epoxy resins, the most either due to extended times or higher temperatures, such as common of which are the polyglycidyl ethers of polyhydric lC. phcnolssuch as the diglycidyl ether of 2,2-bis p-hydroxyphen- As indicated, the inhibitor inhibits crystallization of mix yl propiinc, (bisphenol A), which resin has the following tures of the epoxy resins with water, reactive diluents, solvents theoretical structural formula and fillers which tend to aggravate the crystallization problem,

0 Ull Oil (1 where n is 0 or an integer up to about 2. Generally speaking, n especially when the mixtures are subjected to fluctuations in will usually be no greater than 1. However, other types of temperature. By reactive diluents are meant diluents such as epoxy resins may be employed. Also included are the reaction monoepoxides commonly introduced to change the properties products of other olyhydric phenols with polyfunctional of the cured epoxy resins. Such diluents commonly added to halohydrlhs- Typical Polyhydric Phenols hsefulih the P p 60 the diglycidyl ethers of bisphenol A include monoepoxides tion of such resins include resorcinol and various bisphenols u h a butyl glycidy] ether, phenyl glycidyl ether, cresyl resulting from the condensation of Phehol with aldehydes and glycidyl ether, allyl glycidyl ether and gamma-butyral-octane. ketohes Such as formaldehyde, aeetaldehyde, methyl ethyl One commonly used reactive diluent is Epoxide 8 supplied by k and the like- Procter and Gamble which is a mixture of aliphatic hydrocar- Other types of epoxy resins which may be used and which monoepoxides g y y ethers) in which are commercially available epoxy materials are th hydrocarbon group contains from 12-14 carbon atoms. Orpolyglycidyl ether of t tra h nol whi h hav two hydro ganic solvents, generally non-reactive with the epoxy resin, aryl groups at each end of an aliphatic chain. These which may be used in the preparation of epoxy resins and polyglycidyl ethers are obtained by reacting the tetraphenols which tend to induce crystallization include lower aromatic with polyfunctional halohydrins suchasepichlorohydrin. The hydrocarbons such as benzene, toluene and xylene; lower tetraphenols used in preparing the polyglycidyl ethers are a aliphatic and cycloaliphatic ketones such as acetone, methyl known class of compounds readily obtained by condensing the ethyl ketone, diisobutyl ketone, cyclohexanone and methyl: appropriate dialdehyde with the desired phenol. Typical cyclohexanone; and aliphatic esters of lower monocarboxylic' tetraphenols useful in the Preparation of these p y resins acids such as ethyl acetate, isopropyl acetate, butyl acetate are h alpha, lp g g r i (hy r xyph nyl) and the like. Fillers which induce the crystallization include. alkaneS, Such as ,1, ,2- y yp y ethane, talc, silica, alumina, titanium dioxide and calcium carbonate.

The invention can best be illustrated by means of the following example in which for exemplification one of the most commonly available epoxy resins was employed.

EXAMPLE A liquid epoxy resin, the diglycidyl ether of 2,2-bis (phydroxyphenyl) propane, having an epoxy equivalent weight of about l90, was heated to 125C. and 0.08 parts by weight per 100 parts epoxy of 2-amino-2-ethyl-l,3-propanediol (AEPD) was hand stirred into the heated epoxy. Initially, the mixture was cloudy but cleared as inhibitor was added. The mixture was maintained at 125C. for minutes without any effect on color.

For crystallization studies, samples were prepared with a reactive diluent, and water (50 percent solids emulsion). All samples were 100 gram amount samples. Control samples employing no inhibitor and comparison samples containing a conventional inhibitor, tris(hydroxymethyl) aminomethane (Tl-1AM) were also prepared.

The samples with reactive diluent were prepared by blending 85 parts of the epoxy resin with parts of reactive diluent (Epoxide 8). There was also added 5 parts of polyoxyethylene sorbitan monolaurate (Tween The 50 percent solids in water emulsions were prepared by blending equal parts of epoxy resin (with diluent) and water.

In order to shorten or accelerate the crystallization times for the purposes of the test, the samples were seeded with crystals of pure diglycidyl ether of bisphenol A.

In testing for crystallization, the samples were cycled between room temperature (about C.) and 4C. A typical cycle would be as follows:

a. at 3:30 pm, place samples in refrigerator at 4C.

b. at 8:00 a.m., remove from refrigerator and allow to come to room temperature (about 25C.)

c. at 3:30 p.m., place samples back into the refrigerator.

Each sample was then observed for crystallization on reaching room temperature after removal from the refrigerator. lf crystals were observed in any amount, a failure and the time to crystallization was noted.

The results of the tests are as summarized below:

A. Samples of epoxy resin with diluent:

1. Without inhibitorcrystallized within 4-6 weeks.

2. With THAM inhibitor (0.08 phr) began light crystallization at the 13th week. .3. With AEPD inhibitor (0.08 phr) showed no crystallization after 13 weeks and test continues. B. Samples of 50 percent solids emulsion:

1. Without inhibitor crystallization in 3-12 days.

2. With THAM inhibitor (0.08 phr) crystallization at 2 weeks.

3. With AEPD inhibitor (0.08 phr) crystallization at 3.5 weeks. At 0.08 phr of AEPD inhibitor, crystallization was inhibited for 7 weeks.

The embodiments of the present invention in which an exclusive property or privilege is claimed are defined as follows:

1. A crystallimtion inhibited epoxy resin composition comprising a liquid epoxy resin and a minor amount sufiicient to inhibit crystallization of 2-amino-2-ethyl-l,3-propanediol, said minor amount being an amount of about 002-310 parts by weight per parts of said liquid epoxy resin and wherein said liquid epoxy resin is a poly glycidyl ether of a polyhydric phenol.

2. A composition as defined in claim 1 wherein said liquid epoxy resin is the diglycidyl ether of 2,2-bis( p-hydroxyphenyl) propane.

3. A crystallization inhibited epoxy resin composition comprising an emulsion of a polyglycidyl ether of a polyhydric phenol liquid epoxy resin in water and from about 0.02-3.0 parts hundred parts of resin by weight of 2-amino-2-ethyl-l,3 propanediol.

4. A composition as defined in claim 3 wherein said emulsion comprises about 50 percent concentration by weight of said liquid epoxy resin in water.

5. A composition as defined in claim 3 wherein said epoxy resin is the diglycidyl ether of 2,2-bis( p-hydroxyphenyl) propane.

6. A crystallization inhibited epoxy resin composition comprising a polyglycidyl ether of a polyhydric phenol liquid epoxy resin, a reactive diluent and from about 0.02-3 parts by weight of 2-amino-2-ethyl-l,3-propanediol per 100 parts of said liquid epoxy resin.

7. A composition as defined in claim 6 wherein said liquid epoxy resin is the diglycidyl ether of 2,2-bis(p-hydroxyphenyl) roane. pp *xws r 

2. A composition as defined in claim 1 wherein said liquid epoxy resin is the diglycidyl ether of 2,2-bis(p-hydroxyphenyl) propane.
 3. A crystallization inhibited epoxy resin composition comprising an emulsion of a polyglycidyl ether of a polyhydric phenol liquid epoxy resin in water and from about 0.02-3.0 parts hundred parts of resin by weight of 2-amino-2-ethyl-1,3-propanediol.
 4. A composition as defined in claim 3 wherein said emulsion comprises about 50 percent concentration by weight of said liquid epoxy resin in water.
 5. A composition as defined in claim 3 wherein said epoxy resin is the diglycidyl ether of 2,2-bis(p-hydroxyphenyl) propane.
 6. A crystallization inhibited epoxy resin composition comprising a polyglycidyl ether of a polyhydric phenol liquid epoxy resin, a reactive diluent and from about 0.02-3 parts by weight of 2-amino-2-ethyl-1,3-propanediol per 100 parts of said liquid epoxy resin.
 7. A composition as defined in claim 6 wherein said liquid epoxy resin is the diglycidyl ether of 2,2-bis(p-hydroxyphenyl) propane. 